The present invention relates to a process for manufacturing a covering for an opening in a flexibly curving container wall, in which a pull-tab is laid over the opening and over an area bordering the wall, the pull-tab being adhered to the surface of the wall so that the opening is sealed along its perimeter.
The present invention relates further to an apparatus for manufacturing the covering, comprising a pull-tab for an opening in a flexibly curving container wall. The apparatus comprises a device for applying the pull-tab to the surface of the wall over and beyond the opening, and a device for adhering the pull-tab to the surface of the wall.
The present invention relates further to the covering for an opening in a flexibly curving container wall with a pull-tab which covers the opening and the area bordering the wall, the pull-tab being adhered to the surface of the wall in peripheral direction of the opening by a continuous sealing seam.
German published patent application 40 31 472 describes a container where a pull-tab, applied before filling, seals closed an opening of a container after filling. The pull-tab is hereby first adhered to a place on the container wall beside the opening. This localized adhesion is effected such that the opening remains uncovered for the purpose of subsequent filling. After filling, the pull-tab is laid over the opening and adhered to the surface of the container wall bordering thereto. Depending on the type of material used, the wall tends to curve when the pull-tab is applied. This can lead to problems when covering the opening.
It is an object of the present invention to exactly cover with a pull-tab an opening set in a flexibly curving wall.
The foregoing object has been achieved in accordance with the present invention that the pull-tab follows the curve of the wall. In the apparatus of the present invention, the object is further achieved in that the application device and/or the adhering device can follow the curve direction. In the covering of the present invention, the object has been achieved in that a section, bordering the periphery of the pull-tab in the direction of the opening, and/or a section, comprising a protective covering for the edge of the opening are excluded from the course of the sealing seam.
The present invention has the advantage of enabling a secure and exact closing of an opening by a pull-tab on the wall of a container. The present invention can be used for all container walls made of a flexible material where a pull-tab is applied. The pull-tab can be applied to a wall of a completed container or to a wall from which a container is to be made. Also the container can comprise one wall or a plurality of walls together; and the configuration of the container is not of importance.
The present invention is especially suited to containers where the wall, to which the pull-tab is applied, is made of cardboard. Other materials, however, for example plastics, which curve when the pull-tab is applied, can also be used.
In the apparatus according to the present invention, the devices for applying the pull-tab and/or adhering same to the wall, are placed on the pull-tab. The devices follow the curving movement of the wall which is caused by the application of the pull-tab, which is why they remain constantly in a fixed position on the pull-tab while they carry out their respective procedural steps. The pull-tab adapts to the changed shape of the wall caused by curving.
It is particularly advantageous when the application device and/or the adhering device comprises an application surface which can be pressed against the wall, and whose outer contour is adapted to the contour of the flexible wall. The application surface rests over a large surface area against the pull-tab. The pull-tab adapts to the form of the curved wall caused by the pressure from the application surface, and covers, as a result of the outer shape of the application surface, a large surface area of the wall.
It is further advantageous when the application surface of the application device is formed by the peripheral surface of a spherical roller, which can be guided over the pull-tab with a direction component which extends along the surface of the wall. This results in a close application of the pull-tab onto the surface of the wall, so that good conditions for a later adhering of the pull-tab are created. It is not necessary here for the spherical roller to be guided over the entire length of the pull-tab.
In an advantageous embodiment, the application surface of the adhering device is curved convexly. This convex curve corresponds advantageously to the concave curve of the wall, which arises when the application device and/or the adhering device are pressed against the wall.
In a further advantageous embodiment, the application surface of the adhering device can be heated for the purpose of heat sealing, and is formed with a smaller surface area than the pull-tab. These measures reduce the requirements for an exact guiding of the adhering device. Even if the adhering device should be deflected when being guided to the curving wall, it will still not reach beyond the pull-tab and into the area of the wall surface. Thus the danger of the surface of the wall being damaged due to the high temperatures of the adhering device is avoided.
It is especially advantageous when the application surface of the adhering device comprises a recess which corresponds to the line of a protective covering surrounding the edge of the opening. Due to these measures, the danger of the protective covering adhering to the pull-tab is avoided. Such an adhesion could lead to possible later damage of the protective covering when the pull-tab is removed.